Multi-layer optical disc, and recording method and apparatus for multi-layer optical disc

ABSTRACT

Each layer includes a data recording area and a test writing area divided into a plurality of small areas, wherein the small areas of the test writing area are recorded in advance so that other each layer can make a combination of recorded and unrecorded states with respect to the small area, where OPC is carried out, in a layer where OPC is carried out. Moreover, OPC is carried out to each small area, where a combination of recorded/unrecorded states of other each layer differs from each other, to thereby calculate, as the optimum power, an average value of the result of each OPC or a central value of the dispersion thereof.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/862,231, filed Sep. 27, 2007, now U.S. Pat. No. 7,869,317, thecontents of which are incorporated herein by reference.

INCORPORATION BY REFERENCE

The present application claims priority from Japanese applicationJP2006-291968 filed on Oct. 27, 2006, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to multi-layer optical discs, and inparticular relate's to a method of calculating an optimum value of alaser power for recording into a multi-layer optical disc.

In the case where information is recorded into an optical disc having anonce-writable or rewritable multi-layer structure, a method ofJP-A-2000-311346 is known as the method of adjusting the laser outputduring recording to an optimum recording power value with respect to adata area of a layer, to which information is written (Optimum PowerControl, hereinafter, referred to as “OPC”).

SUMMARY OF THE INVENTION

When recording information by irradiating a multi-layer optical discwith a laser beam, a difference will arise in the transmissivity of anupper layer depending on whether the upper layer near an incident planeof the laser beam is recorded or unrecorded, and therefore even if alaser beam with the same power is emitted, the power of the laser beamsupplied to a lower layer away from the incident plane will vary.Moreover, the optimum recording power may fluctuate due to an effect ofa cross talk from the information recorded in other recording layer.

In JP-A-2000-311346, OPC in a “trial writing area of a lower layer” iscarried out with a laser beam passing through a “test writing area of anupper layer” where a random pattern is recorded. However, the “optimumrecording power value” calculated in this manner is not a suitable onewhen recording into a “data area of the lower layer” with a laser beampassing through an unrecorded “data area of the upper layer”.

In recent years, an optical disc that can record a data into any layerof a multi-layer optical disc has been introduced. In the data area ofan upper layer of such optical disc, an area where a data is recordedand an area where a data is not recorded may coexist. For this reason,when recording a data into a lower layer, there are a case where a datais recorded into a “data area of the lower layer” with a laser beampassing through an unrecorded “data area of the upper layer” and a casewhere the data is recorded into a “data area of the lower layer” with alaser beam passing through a recorded “data area of the upper layer”.However, since the “optimum recording power value” calculated in the OPCof JPA-2000-311346 is the optimum value for either one of theabove-described cases, the “optimum recording power value” is noteffective for the other case, thus causing a problem of not contributingto an improvement in the recording quality of data in either one of thecases.

The above-described problem is solved by the inventions described in theclaims.

According to the present invention, even if recording is carried outrandomly to a multi-layer disc and the recorded portion and unrecordedportion in each layer are randomly distributed and the transmissivitybecomes random, it is possible to write with a favorable power andimprove the recording quality of the data.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a first embodiment that is a multi-layeroptical disc of the present invention.

FIG. 2 is a view showing a second embodiment that is a method ofmanufacturing the multi-layer optical disc of the present invention.

FIG. 3 is a view showing a third embodiment that is a recording methodfor the multi-layer optical disc of the present invention.

FIG. 4 is a view showing a fourth embodiment that is a recording methodfor the multi-layer optical disc of the present invention.

FIG. 5 is a view showing a fifth embodiment that is a recordingapparatus for the multi-layer optical disc of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A multi-layer optical disc that is a first embodiment of the presentinvention is described with a recording type optical disc having a fourlayer structure being as an example, using FIG. 1.

FIG. 1 is a cross sectional view of a multi-layer optical disc, which isrecordable or reproducible from one side, where the right side is aninner peripheral side of the optical disc and the left side is an outerperipheral side of the optical disc. A laser beam for recording into orreproducing from each layer of this optical disc is incident from theabove. Hereinafter, these layers are referred to as a first layer, asecond layer, a third layer, and a fourth layer in this order from theone nearest to the incident plane of the laser beam.

Each layer has, as the recordable areas, a test writing area PCA (PowerCalibration Area) where OPC is carried out to calculate an optimumpower, and a data recording area to which a user data is written.Namely, in FIG. 1, there are four PCAs: the PCA for the first layer; thePCA for the second layer; the PCA for the third layer; and the PCA forthe fourth layer. The PCA of each layer is segmented into a plurality ofsmall areas, such as a, b, c, d, e, f, g, h, sequentially in the radialdirection, in this order from the inner periphery. Note that although inthis embodiment the description will be made assuming the PCA of eachlayer is provided spirally, the PCA may be provided concentrically.

As shown in FIG. 1, all the areas a to h of the PCA for the fourth layerare unrecorded, while a random pattern is recorded in the PCA used forthe first layer, the PCA used for the second layer, and the PCA used forthe third layer as shown in Table 1.

TABLE 1 Random pattern PCA used for first PCA used for second PCA usedfor layer layer third layer Area a recorded unrecorded unrecorded Area brecorded recorded unrecorded Area c recorded recorded recorded Area dunrecorded recorded unrecorded Area e unrecorded unrecorded recordedArea f recorded unrecorded recorded Area g unrecorded recorded recordedArea h unrecorded unrecorded unrecorded

By recording a random pattern into the PCAs of the first layer to thethird layer in accordance with Table 1, all the combinations can beprepared with respect to the recorded/unrecorded states of the PCA usedfor the first layer to the PCA used for the third layer.

If OPC is carried out to the eight areas a to h of the PCA used for thefourth layer, then an optimum value of the recording power in all thecombinations of the recorded/unrecorded states in the first layer to thethird layer can be known, all the combinations occurring at the time ofrecording into the data recording area of the fourth layer of theoptical disc, the optical disc allowing for a random recording. Then,recording of the fourth layer by the use of an average value of theoptimum recording power in each combination facilitates execution ofrecording with an appropriate recording power with respect to the datarecording area of the fourth layer.

Similarly, eight areas corresponding to a combination of therecorded/unrecorded states of the second layer to the fourth layer areprepared in the PCA of the first layer, and eight areas corresponding toa combination of the recorded/unrecorded states of the first layer,third layer, and fourth layer are prepared in the PCA of the secondlayer, and eight areas corresponding to a combination of therecorded/unrecorded states of the first layer, second layer, and fourthlayer are prepared in the PCA of the third layer, and therecorded/unrecorded states are arranged appropriately in each area, andthereby with respect to any one of the first layer to the third layer,all the combinations of the recorded/unrecorded states of other layerscan be prepared.

If the PCA is segmented into 32 areas (4×2⁴⁻¹) in this manner, it ispossible to provide an optical disc with all the combinations of therecorded/unrecorded states of other three layers, all the combinationspossibly occurring at the time of recording into any recording layer ofa recording type optical disc having four layers. In addition, if thisis generalized, in the case of an optical disc having m layers it shouldbe appreciated that m×2^(m-1) areas just need to be prepared in advance.

In the foregoing, a combination of the recorded/unrecorded states of thelower recording layers away from the incident plane of a laser beam isalso taken into consideration, so that the PCA is segmented into 32areas. However, because an effect, which a cross talk from the lowerrecording layer has, at the time of recording into the upper recordinglayer is small, the PCA may be segmented taking into consideration onlythe recorded/unrecorded states of the upper recording layer. In otherwords, a total of 14 areas consisting of two areas used for the secondlayer taking into consideration the first layer, four areas used for thethird layer taking into consideration the first layer to the secondlayer, and eight areas used for the fourth layer taking intoconsideration the first layer to the third layer may be prepared,thereby appropriately arranging the recorded/unrecorded states in eacharea.

If the PCA is segmented into 14 areas in this manner, it is possible toprovide an optical disc with all the combinations of therecorded/unrecorded states of the upper layers, all the combinationspossibly occurring at the time of recording into any recording layer ofa recording type optical disc having four layers.

In addition, in the foregoing an optical disc having a four layerstructure has been described as an example, but the application targetof the present invention is not limited thereto, and the presentinvention can be applied also to an optical disc having any number ofrecording layers.

For example, when a total number of recording layers is m, if each PCAof the first layer to the (m−1)th layer is segmented into 2^(m-1) areas,then all the combinations of the recorded/unrecorded states from theupper first layer to the (m−1)th layer, all the combinations possiblyoccurring at the time of recording into the m-th layer, can be prepared.Moreover, if each PCA of the first layer to the (m−2)th layer issegmented into 2^(m-2) areas, then all the combinations of therecorded/unrecorded states from the upper first layer to the (m−2)thlayer, all the combinations possibly occurring at the time of recordinginto the (m−1)th layer, can be prepared. Similarly, if the PCA of thefirst layer is segmented into 2¹ areas, then all the combinations of therecorded/unrecorded states, all the combinations possibly occurring atthe time of recording into the upper second layer, can be prepared.

Namely, when the number of recording layers is m, if the PCA of eachlayer is segments into (2^(m-1)+2^(m-2)+ . . . +2²+2¹) areas, then allthe combinations of the recorded/unrecorded states of the upperrecording layers, all the combinations possibly occurring at the time ofrecording into any recording area, can be prepared in advance.

According to the first embodiment described above, it is possible toprovide an optical disc including all the combinations of therecorded/unrecorded states in advance, all the combinations possiblybeing taken by the recording layers, through which the laser beam, whenrecording into any recording layer, passes until reaching this relevantrecording layer. Then, if this optical disc is used, it is possible toeasily carry out the recording power control described later, and alsopossible to provide a multi-layer optical disc suitable for calculatingthe recording power control that appropriately addresses a fluctuationin the optimum recording power caused by a variation in thetransmissivity of the upper layer or a cross talk from the adjacentlayer.

In addition, although in this embodiment an example has been shown, inwhich a random pattern is recorded in advance in a portion serving as arecorded area, a specific pattern may be recorded therein. With thisconfiguration, a process to generate the random recording pattern can beomitted in manufacturing the optical disc.

Moreover, although in this embodiment an example has been shown, inwhich the PCA is located on the inner peripheral side of the datarecording area, the PCA may be located on the outer peripheral sidethereof or may exist on the both sides. With this configuration, the useof the PCA provided on the outer peripheral side allows a multi-layeroptical disc capable of test writing at a recording rate different fromthat of the test writing on the inner peripheral side to be provided.

Moreover, in this embodiment an optical disc has been described, whichstores all the combinations for the recorded/unrecorded states of theupper layers, however, an optical disc may be employed, which includesonly a combination where all the PCAs of the upper layers are “recorded”and a combination where all the PCAs of the upper layers are“unrecorded”. If this optical disc is employed, an optimum recordingpower in a situation where the transmissivity is highest and an optimumrecording power in a situation where the transmissivity is lowest can becalculated easily, and an average value of the both can be alsocalculated easily.

FIG. 2 is a flowchart showing a second embodiment that is a method ofmanufacturing the multi-layer optical disc described as the firstembodiment. This flowchart shows among the manufacturing steps aportion, in which PCAs are initialized for the purpose of OPC after themulti-layer optical disc is manufactured as a writable area in theordinary manufacturing process.

Step 201 represents a step to divide the PCA into y areas used for eachlayer. In the case of the optical disc having a four layer structureshown in the first embodiment, y is four.

Step 202 represents a step to re-divide the y-divided PCA into X areasused for each layer (m-th layer). If all the combinations of recordedand unrecorded areas are provided in the optical disc having a fourlayer structure shown in the first embodiment, then X=8.

Step 203 represents a step, in which a random pattern is written to theeach X-divided areas used for the m-th layer so that the combinations ofthe recorded and unrecorded states in each layer of each area may differfrom each other. In the case of the optical disc having a four layerstructure shown in the first embodiment, for example, this stepcorresponds to the step of sequentially writing a random pattern fromthe area a with respect to the areas a to h of the PCA used for thefourth layer.

Step 204 represents a step, in which it is determined whether theprocessing of Step 203 has been completed with respect to all the PCAsused for all the layers, and if not completed yet, Step 203 is carriedout again, and if completed, the process of preparing PCA areas isterminated. In the case of the optical disc having a four layerstructure shown in the first embodiment, it is determined whether allthe combinations of recorded and unrecorded states in each layer havebeen prepared with respect to the PCA used for the fourth layer, PCAused for the third layer, PCA used for the second layer, and PCA usedfor the first layer.

According to this embodiment, even in the case where a difference in thetransmissivity might occur or an effect or the like of a cross talkmight occur depending on whether the other layer is recorded orunrecorded, execution of a random access, including the random accessbetween layers, in a multi-layer disc allows for OPC corresponding toeach case, so that even in a disc allowing for a random access, it ispossible to manufacture a disc that can record with an appropriaterecording power. Moreover, in this embodiment an example has been shown,in which for each area, writing of a random pattern is carried outselectively with respect to all the layers, however, for each layer,writing of a random pattern may be carried out selectively with respectto the areas, in this order. Moreover, it is possible to manufacture adisc that can record with an appropriate recording power using themethod shown in this embodiment by recorder for the multi-layer opticaldisc.

FIG. 3 is a flowchart showing a third embodiment that is a recordingmethod for the multi-layer optical disc described as the firstembodiment.

In Step 301, the position of a pickup is aligned with the n-th area ofthe PCA used for the m-th layer. In the case of the first embodiment,the position of the pickup is aligned with the area a, first.

In Step 302, OPC is executed. Specifically speaking, recording iscarried out by changing the recording power successively and then anarea where the recording was carried out is reproduced, and a recordingpower at which the reproduction quality becomes the best is selected asthe optimum recording power. The judgment on the reproduction quality ismade by using the error rate, jitter, waveform (e.g., β), or the like.

In Step 303, n=n+1 for the purpose of changing the area is carried out.Namely, in combination with Step 301, the area will be changedsuccessively. Step 301 and Step 303 combined will change the position ofthe pickup from the area a, b, c, . . . in this order, in the case ofthe first embodiment.

In Step 304, it is determined whether the OPC has been executed withrespect to all the combinations used for the m-th layer, and if notcompleted yet, the flow will return to Step 301 to continue the flow,and if completed, the flow will proceed to the next step 305. In thecase of the first embodiment, it will be determined whether the OPC hasbeen done in all the areas a, b, c, d, e, f, g, and h.

In Step 305, an average value of the OPC results with respect to all thecombinations of the recorded or unrecorded states of the other layerswith respect to the m-th layer is calculated. In the first embodiment,an average value of the OPC results with respect to all the areas a, b,c, d, e, f, g, and h is calculated.

In Step 306, the average value calculated in Step 305 is registered asthe optimum recording power of the m-th layer.

According to this embodiment, even if a random access, including therandom access between the layers, is allowed in a multi-layer opticaldisc, the optimum recording power can be calculated. Specifically, byexecuting OPC in this manner, it is possible to calculate an appropriatelaser power with respect to all the combinations possibly occurring atthe time of recording into a desired recording layer, and also possibleto carry out recording using the appropriate laser power calculated byOPC even when randomly recording into any recording layer.

In addition, in this embodiment the OPC of the m-th layer has beendescribed, the same is true of other layer. Moreover, in thisembodiment, with respect to the PCA used for the m-th layer, all thecombinations of recorded/unrecorded states of the other layers areprovided and then the OPC is carried out to all the combinations tocalculate an average value, however, from a viewpoint of transmissivity,with respect to the PCA used for the m-th layer, all the combinations ofthe recorded and unrecorded states of the upper layers or a combinationof areas selectively selected may be provided to carry out OPC andcalculate an average value. Moreover, although in this embodiment anadjustment of the optimum power has been made with respect to eachcombination, an adjustment of the recording waveform may be furthermade. Moreover, although in this embodiment a configuration has beenshown, in which an optimum recording power, which is an average value,is employed as the optimum recording power of the m-th layer, a centralvalue of the optimum value dispersion may be used in place of using theaverage value.

FIG. 4 is a flowchart showing a fourth embodiment that is a recordingmethod for the multi-layer optical disc described as the firstembodiment. In FIG. 4, Step 301, Step 302, Step 303, and Step 304 aresimilar to those of the third embodiment, so the descriptions thereofare omitted. In this embodiment, with respect to the PCA used for them-th layer, all the combinations of the recorded and unrecorded statesof the other layers are provided to carry out OPC to all thecombinations. Hereinafter, the description is made in detail.

In Step 401, the maximum value and the minimum value of the results ofthe OPC with respect to all the combinations of the recorded orunrecorded state of the other layers with respect to the m-th layer arecalculated.

In Step 402, an average of the maximum value and the minimum value iscalculated.

In Step 306, as in the third embodiment, the calculated average value isregistered as the optimum recording power of the m-th layer.

As described above, according to this embodiment, even if a randomaccess, including the random access between the layers, is allowed in amulti-layer optical disc, the optimum recording power can be calculated.In addition, although in this embodiment the OPC of the m-th layer hasbeen described, the same is true of other layer. Moreover, also in thisembodiment, with respect to the PCA used for the m-th layer, all thecombinations of the recorded and unrecorded states of the other layersare provided to carry out OPC, however, as in the third embodiment, withrespect to the PCA used for the m-th layer, all the combinations of therecorded and unrecorded states of the upper layers or a combination ofareas selectively selected may be provided to carry out OPC. Moreover,it is also possible to carry out OPC only to an area having the maximumvalue and an area having the minimum value among the combinations of therecorded and unrecorded states, taking into consideration thetransmissivity. Moreover, although in this embodiment an adjustment ofthe optimum power has been made with respect to each combination, anadjustment of the recording waveform may be further made.

FIG. 5 is a block diagram showing a fifth embodiment that is a recordingapparatus for the multi-layer optical disc of the present invention.

In FIG. 5, reference numeral 501 represents an optical disc, referencenumeral 502 represents a disc motor for rotating the optical disc 501,reference numeral 503 represents a laser that emits light for readingfrom and writing to the optical disc 501, reference numeral 504represents an optical pickup having the laser 503 and further having alens for focusing the laser beam on the optical disc, and an OEIC(optical electronic IC) for converting an optical signal into anelectric signal, and reference numeral 505 represents a signalreproduction processing circuit, which carries out waveform equalizationto a signal detected in the optical pickup 504, and reproduces asynchronous clock. The signal reproduction processing circuit furtherdetects jitter at each edge.

Reference numeral 506 represents a test-write reproduction signalprocessing circuit, which carries out the processing shown in Step 302of the third embodiment, i.e., the derivation of the optimum recordingpower for a defined area, on the basis of jitter detected in the signalreproduction processing circuit 505. Reference numeral 507 represents anoptimum power storing circuit, which stores the optimum recording powerfor each area derived in the test-write reproduction signal processingcircuit 506. Reference numeral 508 represents an average calculationcircuit, which calculates an average of the optimum power for each areastored in the optimum power storing circuit 507 and sets this to theoptimum recording power of a target layer. In addition, in thisembodiment, the optimum recording power storing circuit 507 and theaverage calculation circuit 508 are provided inside an optimum recordingpower calculation circuit 515.

Reference numeral 509 represents a servo control circuit, which carriesout the rotation control of the disc motor and the focusing and trackingcontrol of the light beam. Reference numeral 510 represents a laser beamcontrol circuit, which controls the light emission intensity of thelaser 503. Reference numeral 511 represents a test-write recordingsignal processing circuit, which generates a signal pattern for trialwriting to PCA. In this embodiment, the test-write recording signalprocessing circuit generates a random pattern, for example. In addition,in this embodiment, the test-write recording signal processing circuit511 along with the test-write reproduction signal processing circuit 506are provided inside a test write processing circuit 514. Referencenumeral 512 represents a recording signal processing circuit, whichexecutes the addition of an error correcting code and the modulationprocessing when writing a user data into a data recording area.Reference numeral 513 represents a CPU, which controls the signalreproduction processing circuit 505, the test-write reproduction signalprocessing circuit 506, the servo control circuit 509, the laser beamcontrol circuit 510, the test-write recording signal processing circuit511, and the recording signal processing circuit 512, and which alsouses an output of the average calculation circuit 508 for controllingthe laser beam control circuit 510.

Hereinafter, an operation when the recording apparatus of thisembodiment records into the optical disc of the first embodiment usingthe recording method of the third embodiment is described.

First, corresponding to Step 301 of the third embodiment, the pickup ismoved to the area a of the m-th layer under the control of the servocontrol circuit 509.

Next, corresponding to Step 302, two processings of writing and readingare carried out. First, in the writing process, the recording apparatusrecords a random pattern within this area, the random pattern beinggenerated in the test-write recording signal processing circuit 511,while successively changing the light emission power of the laser 503 bymeans of the laser beam control circuit 510. In the reading process tobe carried out next, the recorded signal is reproduced and detected inthe optical pickup 503, and from this detected signal the jitter foreach light emission power is detected in the signal reproductionprocessing circuit 505. The test-write reproduction signal processingcircuit 506 calculate the light emission power minimizing the jitter tothe optimum recording power, and stores this result in the optimum powerstoring circuit 507. A control to return from Step 303 to Step 301 viaStep 304 is achieved by that the servo control circuit 509 successivelymoves the pickup to the area a, b, c, d, . . . of the first embodiment.

Corresponding to Step 304, when the CPU determined that the OPC in allthe combinations has been completed, i.e., when the OPC in the areas ato h has been completed, the average calculation circuit 508 calculatesan average of the results of the area a to the area h stored in theoptimum power storing circuit 507, corresponding to Step 305.

Subsequently, corresponding to Step 306, the average value calculated inthe average value calculation circuit 508 is sent to CPU 513 as theoptimum recording power of the relevant m-th layer, and when recording auser data into the data recording area of the relevant m-th layer, thelaser beam control circuit is controlled based on the optimum power sentto CPU 513.

As described above, according to this embodiment, it is possible toprovide a recording apparatus that can calculate the optimum recordingpower in each layer with respect to a multi-layer recording optical discthat allows for a random access, including the random access betweenlayers as well.

In addition, in this embodiment, a case has been described, in which theevaluation of the reproduction quality of a test-written signal is madeusing jitter, however, when the evaluation is made using waveforminformation, such as β, the detection of β is made in the signalreproduction processing circuit 505, and the light emission powerproviding a target β value is set to the optimum recording power in thetest-write reproduction signal processing circuit 506. Moreover,although in this embodiment an adjustment of the optimum power is made,an adjustment of the recording waveform may be further made. In thiscase, the recording waveform is controlled by the laser beam controlcircuit 509.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A multi-layer optical disc having m (m is an integer equal to orlarger than 3) recording layers, which is arranged in a manner that atleast 1^(st) to k-th small areas (k is an integer of 2^(b-1)) areprovided as to a b-th recording layer (b is an integer from 2 to m) tothereby provide n (n≧2^(m-1)+2^(m-2)+ . . . +2²+2¹) small areas in totalas to 2^(nd) to m-th recording layers, and recording is performed in amanner that with respect to the 1^(st) to k-th unrecorded small areas ofthe b-th recording layer, a combination of recorded/unrecorded states ofdata in (b−1) small areas at a radius position of a (b−1)-th recordinglayer nearer to an incident plane of a laser beam than the b-threcording layer differs from a combination of recorded/unrecorded statesof data in (b−1) small areas at another radius position of the (b−1)-threcording layer.
 2. A multi-layer optical disc according to claim 1,wherein the multi-layer optical disc is recorded in a manner that, afterthe recording in the manner that the combination of recorded/unrecordedstates of data in (b-1) small areas at the radius position of the(b-1)-th recording layer differs from the combination ofrecorded/unrecorded states of data in (b-1) small areas at the anotherradius position of the (b-1)-th recording layer, recording the 2^(b-1)small areas of the b-th recording layer with a plurality of recordingpowers at the time of the recording when recording in the manner thatthe combination of recorded/unrecorded states of data in (b-1) smallareas at the radius position of the (b-1)-th recording layer differsfrom the combination of recorded/unrecorded states of data in (b-1)small areas at the another radius position of the (b-1)-th recordinglayer; and recording quality of data of a predetermined layer recordedwith the plurality of recording powers is evaluated.
 3. A recordingmethod for a multi-layer optical disc having m (m is an integer equal toor larger than 3) recording layers, the method comprising: providing atleast 1 ^(st) to k-th small areas (k is an integer of 2^(b-1)) as to ab-th recording layer (b is an integer from 2 to m) to thereby provide n(n≧2^(m-1)+2^(m-2)+. . . +2²+2¹)small areas in total as to 2^(nd) tom-th recording layers, and recording in a manner that with respect tothe 1 ^(st) to k-th unrecorded small areas of the b-th recording layer,a combination of recorded/unrecorded states of data in (b-1) small areasat a radius position of a (b-1)-th recording layer nearer to an incidentplane of a laser beam than the b-th recording layer differs from acombination of recorded/unrecorded states of data in (b-1) small areasat another radius position of the (b-1)-th recording layer; after therecording in the manner that the combination of recorded/unrecordedstates of data in (b-1) small areas at the radius position of the(b-1)-th recording layer differs from the combination ofrecorded/unrecorded states of data in (b-1) small areas at the anotherradius position of the (b-1)-th recording layer, recording the 2^(b-1)small areas of the b-th recording layer with a plurality of recordingpowers at the time of the recording when recording in the manner thatthe combination of recorded/unrecorded states of data in (b-1) smallareas at the radius position of the (b-1)-th recording layer differsfrom the combination of recorded/unrecorded states of data in (b-1)small areas at the another radius position of the (b-1)-th recordinglayer; and evaluating recording quality of data of a predetermined layerrecorded with the plurality of recording powers.
 4. A recording methodfor a multi-layer optical disc having m (m is an integer equal to orlarger than 3) recording layers, the method comprising: with respect tothe multi-layer optical disc which is arranged in a manner that at least1 ^(st) to k-th small areas (k is an integer of 2^(b-1)) are provided asto a b-th recording layer (b is an integer from 2 to m) to therebyprovide n (n≧2^(m-1)+2^(m-2)+. . . +2²+2¹) small areas in total as to2^(nd) to m-th recording layers, and recording is performed in a mannerthat with respect to the 1^(st) to k-th unrecorded small areas of theb-th recording layer, a combination of recorded/unrecorded states ofdata in (b-1) small areas at a radius position of a (b-1)-th recordinglayer nearer to an incident plane of a laser beam than the b-threcording layer differs from a combination of recorded/unrecorded statesof data in (b-1) small areas at another radius position of the (b-1)-threcording layer, recording the 2^(b-1) small areas of the b-th recordinglayer with a plurality of recording powers; and evaluating recordingquality of data of a predetermined layer recorded with the plurality ofrecording powers.
 5. A recording apparatus for a multi-layer opticaldisc having m (m is an integer equal to or larger than 3) recordinglayers, comprising: a laser which irradiates the optical disc with alaser beam; a laser beam control circuit which controls the laser; aunit which, in a case of providing at least 1^(st) to k-th small areas(k is an integer of 2^(b-1)) as to a b-th recording layer (b is aninteger from 2 to m) to thereby provide n (n≧2^(m-1)+2^(m-2)+. . .+2²+2¹)small areas in total as to 2^(nd) to m-th recording layers,records in a manner that with respect to the 1^(st) to k-th unrecordedsmall areas of the b-th recording layer, a combination ofrecorded/unrecorded states of data in (b-1) small areas at a radiusposition of a (b-1)-th recording layer nearer to an incident plane of alaser beam than the b-th recording layer differs from a combination ofrecorded/unrecorded states of data in (b-1) small areas at anotherradius position of the (b-1)-th recording layer; a unit which, after therecording in the manner that the combination of recorded/unrecordedstates of data in (b-1) small areas at the radius position of the(b-1)-th recording layer differs from the combination ofrecorded/unrecorded states of data in (b-1) small areas at the anotherradius position of the (b-1)-th recording layer, records the 2^(b-1)small areas of the b-th recording layer with a plurality of laser powersat the time of the recording when recording in the manner that thecombination of recorded/unrecorded states of data in (b-1) small areasat the radius position of the (b-1)-th recording layer differs from thecombination of recorded/unrecorded states of data in (b-1) small areasat the another radius position of the (b-1)-th recording layer; and aunit which evaluates recording quality of data of a predetermined layerrecorded with the plurality of laser powers.
 6. A recording apparatusfor a multi-layer optical disc having m (m is an integer equal to orlarger than 3) recording layers, comprising: a laser which irradiates alaser beam with respect to the multi-layer optical disc which isarranged in a manner that at least 1^(st) to k-th small areas (k is aninteger of 2^(″)) are provided as to a b-th recording layer (b is aninteger from 2 to m) to thereby provide n (n≧2^(m-1)+2^(m-2)+. . .+2²+2¹)small areas in total as to 2^(nd) to m-th recording layers, andrecording is performed in a manner that with respect to the 1^(st) tok-th unrecorded small areas of the b-th recording layer, a combinationof recorded/unrecorded states of data in (b-1) small areas at a radiusposition of a (b-1)-th recording layer nearer to an incident plane of alaser beam than the b-th recording layer differs from a combination ofrecorded/unrecorded states of data in (b-1) small areas at anotherradius position of the (b-1)-th recording layer; a laser beam controlcircuit which controls the laser; a unit which records the 2^(b-1) smallareas of the b-th recording layer with a plurality of recording powers;and a unit which evaluates recording quality of data of a predeterminedlayer recorded with the plurality of recording powers.